High power miniature demand power supply

ABSTRACT

A miniature power supply and voltage regulator containing a ceramic substrate with conductive metal bonded to the top and bottom of the substrate. The power supply contains a first device for converting alternating current to direct current, a device means for converting alternating current to direct current, a device for determining the current demands of a load, and a device for delivering the current demands to the load. The said power supply and voltage regulator has a power handling capability of at least 23 watts per square inch of surface area.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application is a continuation-in-part of applicants' patentapplication U.S. Ser. No. 08/642,463, filed on May 3, 1996 and now U.S.Pat. No. 5,608,617.

FIELD OF THE INVENTION

A miniature demand power supply and voltage regulator which can handlein excess of 1,000 watts of power.

BACKGROUND OF THE INVENTION

As electronic assemblies becomes more complex and, simultaneously, moreminiaturized, there is a need for components of these assemblies whichcan handle a large amount of power while still retaining their smallsize. Thus, for example, the electronic assemblies in automotive enginesare subjected to a substantial amount of heat, much of which theygenerate themselves; but, because of design dictates, they must berelatively small and light. There are similar needs for miniaturizedcomponents in most modern day electronic equipment.

Electronic components must dissipate a substantial amount of heat theygenerate; excessively high temperatures impair the operation of solidstate components and often destroy them.

Heat dissipation, however, is a function of the thermal conductivity ofelectronic assemblies. The thermal conductivities of these assembliesvaries with the nature of the materials used in them and their mass.

In many applications, power outputs in excess of 1,000 watts arerequired. To the best of applicants' knowledge and belief, the prior artpower supplies which are capable of providing such an output must have asurface area of at least about 64 square inches and often weigh inexcess of five pounds. For many required applications, these devices aretoo large, heavy, and cumbersome.

It is an object of this invention to provide a power supply which issubstantially smaller and lighter than prior art power supplies but canhandle in excess of 1,000 watts of power.

SUMMARY OF THE INVENTION

In accordance with this invention, there is provided a miniature powersupply comprised of a bottom metal ground plane bonded to anintermediate ceramic substrate; the metal is preferably copper (althoughit could be silver, gold, or aluminum), and the ceramic is preferablyalumina (although it could be beryllia, e.g.). Metalized coppercircuitry is preferably bonded to the top of the alumina substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood by reference to thefollowing detailed description thereof, when read in conjunction withthe attached drawings, wherein like reference numerals refer to likeelements, and wherein:

FIG. 1 is a block diagram illustrating one preferred electronic assemblyusing the power supply of the invention;

FIG. 2 is a block diagram of one preferred power supply of thisinvention;

FIG. 3 is a top view of a preferred power board of this invention;

FIG. 4 is a schematic diagram of the preferred power board of FIG. 3;

FIGS. 5, 5A, and 5B are is a schematic diagrams of a preferredcontroller of the power supply of FIG. 2;

FIG. 6 is a top view of a preferred controller board of this invention;

FIG. 7 is a top view of a preferred panel containing four power boardsof this invention;

FIGS. 8A through 8D are sectional views of a substrate as it goesthrough various stages of the preferred process used to make a preferredpower board;

FIG. 9 is a sectional view of a preferred metallized substrateillustrating filled via and empty vent hole structures;

FIG. 10 is a sectional view of a preferred metallized substrateillustrating filled via and filled vent hole structures;

FIG. 11 is a sectional view of a preferred metallized substrate coveredby a dielectric coating;

FIG. 12 is a top view of an individual power board made in accordancewith this invention;

FIG. 13 is a top view of another preferred power board of thisinvention;

FIG. 14 is a schematic diagram of the preferred power board of FIG. 13;

FIG. 15 is a schematic diagram of a preferred controller of the powersupply of FIG. 13;

FIG. 15A is the power supply of the controller of FIG. 15;

FIG. 15B is the clock of the controller of FIG. 15; and

FIG. 15C is the voltage control circuitry of the controller of FIG. 15;

FIG. 16 is a schematic of the driver circuitry of the controller of FIG.15;

FIG. 17 is a top view of another preferred controller board of thisinvention;

FIG. 18 is a top view of a preferred panel containing four power boardsof this invention;

FIG. 19 is a top view of an individual power board made in accordancewith this invention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram illustrating one preferred electronic assemblyusing the power supply/voltage regulator of this invention.

Referring to FIG. 1, it will be seen that electronic assembly 10 iscomprised of a first source of alternating current 12 which providingalternating current via line 14 to power supply/voltage regulator 16.

Alternating current source 12 can be any conventional device whichprovides alternating current. It is preferred that the alternatingcurrent provided by current source 12 provide an root mean squarevoltage of from about plus and minus 1 to about plus and minus 400volts. In a more preferred embodiment, current source 12 provides fromabout plus and minus 1 to about plus and minus 160 r.m.s. volts ofpower.

In one embodiment, single-phase power is supplied by current source 12.In another embodiment, three-phase power is supplied by current source.

Devices for providing single-phase and three-phase alternating currentand voltage outputs are known to those skilled in the art. Thus, by wayof illustration and not limitation, power supply 12 may be one or moreof the conventional power supplies described in U.S. Pat. Nos.5,400,443, 5,436,822, 5,434,738 (three-phase alternating current powersupply), 5,365,146 (high voltage alternating current power supply),5,361,120 (three phase a.c. power supply), 5,355,075 (three phase a.c.power supply), 5,350,959 (alternating current generator), 5,339,255(multi-stage power supply), 5,323,102 (alternator), 5,300,874,5,274,208, 5,032,974 (three-phase power supply), 4,816,985, 4,807,102,4,463,414 (power supply for highly inductive load), 3,577,060, and thelike. The disclosure of each of these United States patents is herebyincorporated by reference into this specification.

Referring again to FIG. 1, and in the preferred embodiment depictedtherein, power supply 12 may be the only source of alternating currentfed into power supply/voltage regulator 16. Alternatively, oradditionally, one may feed a separate alternating current into regulator16 from power supply 18.

In one embodiment, power supply 12 is an alternator whose output rangesfrom about 1 ampere to about 50 amperes and whose rms voltage variesfrom plus and minus 1 volt to plus and minus 200 volts. In thisembodiment, power supply 18 is preferably identical to power supply 16;and its output is transmitted via line 20 to power supply/voltageregulator 16. In another embodiment, not shown, power supplies 16 and 18produce different outputs; in one aspect of this latter embodiment,power supply produces 25 amperes, and power supply 18 produces 50amperes.

As will be apparent to those skilled in the art, although twoalternating current power supplies are illustrated in FIG. 1, only onesuch power can be used, or three such power supplies can be used, orfour or more such power supplies can be used, etc.

Power supply/voltage regulator 16 will convert one or more of theincoming alternating current inputs (such as the inputs from lines 14and 20) to one or more direct current outputs at a defined and regulatedvoltage.

The process of this invention can be used to make many of the powersupply/voltage regulators of the prior art substantially smaller yetstill capable of producing power outputs in excess of 1,200 watts. Thus,by way of illustration, one of the power assemblies of this inventionhas an output about 1224 watts.

Thus, by way of illustration, one may use the blocking-oscillatorswitched mode power supply disclosed in U.S. Pat. No. 5,420,776; theentire disclosure of this patent is hereby incorporated by referenceinto this specification. This power supply is comprised of a transformerhaving a primary winding. A smoothing capacitor is connected to theprimary winding. A bridge rectifier is connected to the smoothingcapacitor. A semiconductor switching element is connected to the primarywinding for the clocked application of the alternating voltage, beingrectified by the bridge rectifier and smoothed by the smoothingcapacitor, to the primary winding.

By way of further illustration, one may use the power supply disclosedin U.S. Pat. No. 5,398,182, the entire disclosure of which is alsoincorporated by reference into this specification. With this powersupply, the rectified output of two or more secondaries are connected inseries and then parallel, each half-cycle of an alternating currentenergization signal. Logic circuitry monitors the rectified output andautomatically switches from a series to a parallel connection to providea regulated power supply output.

By way of yet further illustration, one may use the power supply controlsystem disclosed in U.S. Pat. No. 5,383,140, the entire disclosure ofwhich is hereby incorporated by reference into this specification. Thispower supply control system is usable with portable computer having acentral processing unit and is operable in response to a power supplyfrom a rechargeable battery or alternating current. The control systemincludes a charge unit for charging, current demand detection, and apower control microprocessor for controlling the charge independently ofthe central processing unit.

Thus, by way of further illustration, one may use the alternating,current-fed power supply disclosed in U.S. Pat. No. 4,084,217. Thedisclosure of this patent is also incorporated by reference into thisspecification.

Referring again to FIG. 1, the power supply/voltage regulator preferablyis comprised of certain elements. As will be more readily apparent laterin this specification, it contains a first means for convertingalternating current to direct current, a second means for convertingalternating current to direct current, a means for determining thecurrent demands of a load, and means for delivery such current demandsto said load.

FIG. 2 is a block diagram of one preferred embodiment of the powersupply/voltage regulator 16. Referring to FIG. 2, three-phasealternating current from line 14 is fed to power supply/rectifier 22,which converts such alternating current into one defined direct currentoutput 24; in one embodiment, current output 24 is 28 volts of directcurrent. Current output 24 is preferably fed to load 26.

In one embodiment, load 26 is comprised of a multiplicity of fuelinjector assemblies which control the amount of fuel being fed to aninternal combustion engine; thus, e.g., the load 26 may comprise four,six, eight, or more such fuel injector assemblies. It is preferred thatthe fuel injector assemblies be electric or electronic fuel injectorassemblies, such as those disclosed in U.S. Pat. Nos. 5,427,319(solenoid operated fuel injector), 5,390,493, 5,351,893 (electromagneticfuel injector), 5,322,497, 5,201,299, 5,16,510, 5,147,464, and the like.The disclosure of each these United States patents is herebyincorporated by reference into this specification.

Referring again to FIG. 2, line 28 is a sense line which suppliesinformation to controller 30. Information from controller 30 is passedvia line 32 to signal duplicator 34, which creates three separatecontrol signals from the one signal fed into it via line 32 andthereafter passes these three separate pulsing gate control signals vialine 36 back to power supply/rectifier 22.

Referring again to FIG. 2, alternating current is supplied via line 20to power supply/rectifier 38, which provides substantially the samefunction as power supply/rectifier 22. The output 40 from powersupply/rectifier 38 is supplied to one or more loads 42. Where more thanone load is used, the output feeds such loads in parallel.

Thus, by way of illustration, load(s) 42 may be the lights of anautomobile, and/or its radio, one or more pumps, a television, motordevices, musical instruments, and the like.

In one preferred embodiment, illustrated in FIG. 2, a separate output 42is provided from power supply/rectifier 38 to feed one or more loads 46.

A sense line 48 from power supply/rectifier 38 is used to feedinformation to controller 30 which, in turn, feeds information via line50 to signal duplicator 52, which performs substantially the samefunction as signal duplicator 34. The three outputs from signalduplicator 52 are then fed via line 54 back to control powersupply/rectifier 38.

Power from line 48 is also fed via line 54 to control board power supply56, which converts the voltage to a logic level voltage and then feedsit via line 58 to an oscillator 60. The output from oscillator 60 isthen fed via line 62 to controller 30. Power supply 56 also suppliespower to controller 30 via line 62.

Referring again to FIG. 2, a thermal switch 64 senses when thetemperature of assembly power supply/voltage regulator 16 exceeds aspecified temperature and, when this situation arises, it disconnectspower to signal duplicator 34.

FIG. 3 is a top view of circuit board 23 and a circuit illustratingpreferred embodiments of power supply/rectifiers/regulator 22 and 38.Referring to FIG. 3, the power supply/rectifier on top of lines 70 and72 (which separates the two power supplies/rectifier circuits) is powersupply/rectifier 22; and the power supply rectifier below lines 70 and72 is power supply/rectifier 38. As will be apparent to those skilled inthe art, the components used in the power supply/rectifiers 22 and 38(such as, e.g., diodes, transistors, field effect transistors, andsilicon controlled rectifiers) are "dies" (pieces of silicon chips)which are surface mounted on the circuit board.

FIG. 4 is a schematic of a preferred power supply/rectifier which can beused as power supply/rectifier 22 and/or supplier rectifier 38; dottedline 37 divides the two power supply/rectifier assemblies.

Referring to FIG. 4, and in the preferred embodiment depicted therein,alternating current is input via lines 201, 203, 205, 207, 209, and 211;direct current output is fed via lines 215, 217, and 219.

As will be apparent to those skilled in the art, the preferredembodiments depicted in FIG. 4 are comprised of a multiplicity of diodes(such as D18, D20, D21, etc.), silicon controlled rectifiers (such as,e.g., Q1, Q3, Q6, etc.), and gate control lines 221, 223, 225, 227, 229,and 231.

FIG. 5 is a schematic of the preferred control section 233, whichincludes controller 30, thermal switch 64, signal duplicators 34 and 52,oscillator 60, and power supply 56. Referring to FIG. 5, dotted linesenclose various portions of control section 233 to indicate whether suchportions comprise such controller 30, thermal switch 64, signalduplicators 34 and 52, oscillator 60, and power supply 56. Resistors R39and R40 preferably have minimum resistances of 150,000 ohms and 50,000ohms, respectively, and are actively trimmed to the required circuitvalues.

FIG. 6 is a top view a preferred circuit board comprised of controller30, thermal switch 64, signal duplicators 34 and 52, oscillator 60, andpower supply 54, illustrating the circuit line architecture for thisembodiment. Referring to FIG. 6, the term "SCR" refers to siliconcontrolled rectifiers, the term "AC" refers to an alternating currentinput, the term "T1" refers to one side of the thermal switch 64 input,the term "B+" refers to a battery input, the term "AGND" refers to aground, the term "D" refers to a diode, the various resistive elementsare referred by numbers such as, e.g., "51", "52", etc, the term "Q"refers to a transistor with emitter ("E"), base ("B"), and collector("C"), the term "X" refers to a signal duplicator toroid, and the term"J" refers to a jumper, and the therm "C" followed by a number refers toa specific capacitor. The battery 240 and 242 is provided signalduplicators 34 and 52.

It will be apparent to those skilled in the art that many other circuitarrangements may be used to provide functions similar to those providedby the assembly of FIG. 2.

A Preferred Power Board

FIG. 7 is a top view of a substrate panel 76 which is comprised ofsections 78, 80, 82, and 84 which can be separated along scribe lines 86and 88. In the preferred embodiment illustrated in FIG. 7, each ofsections 78, 80, 82, and 84 are preferably about 2 inches by 2.75inches.

The substrate panel 76 is preferably made from a 96 percent aluminasubstrate in substantial accordance with the procedure described in U.S.Pat. Nos. 5,058,799 and 5,100,714; the disclosure of each of theseUnited States patents is hereby incorporated by reference into thisspecification.

As will be apparent to those skilled in the art, instead of alumina onemay use other substrates such as, e.g., those comprised of berylliumoxide, or of diamond, aluminum nitride, silica containing materials(such as glass), and other ceramic materials conventionally used assubstrates in the printed circuit board industry.

Thus, by way of illustration, and in substantial accordance with theprocedure of U.S. Pat. No. 5,058,799, a metalized substrate may beproduced from a 5.0 by 7.0 inch alumina blank which is 0.025 inchesthick and contains patterned copper on each of its top and bottomsurfaces which is 0.0065 inches thick. The copper circuit pattern usedon the top surface of the substrate is illustrated in FIG. 3.

The metalized substrate may be heat treated in a conventional furnacesuch as, e.g., a conveyor furnace, model number 14CF-154S, which ismanufactured by the Watkins-Johnson company of Scotts Valley, Calif.

In the first stage of the heat treatment, the metalized substrate isheated to a temperature of 635 degrees Fahrenheit for 3 hours in air toform a thin layer of copper oxide on the surface of the copper. An oxidelayer of from about 5 to 50 microinches is formed on the copper.

Thereafter, the oxidized substrate is conveyed through a conventionalfurnace, such as the aforementioned conveyor furnace, while beingcontacted with nitrogen flowing at a rate of from about 5 to about 150cubic feet per minute; during this stage, from about 5 to about 80 partsper million of oxygen are present in the furnace environment. In onepreferred embodiment, from about 10 to about 20 parts per million ofoxygen are present in the atmosphere.

In the first stage of the furnace heating, the temperature is raisedfrom ambient to a temperature of from about 1065 to about 1075 degreesCentigrade over a period of 45 minutes. As will be apparent to thoseskilled in the art, a eutectic melt is formed when the substrate issubjected to temperatures within this range. The temperature may be evenhigher (such as, e.g., higher than 1084, the melting point of copper);in this case, the substrate is exposed to the eutectic range oftemperatures (1065 to 1075) during the ramp up to and the ramp down fromthe highest temperature used in the process. Reference may be had toU.S. Pat. No. 5,058,799, the entire disclosure of which is herebyincorporated by reference into this specification.

Thereafter, the substrate is preferably maintained at the soaktemperature (1065-1075 degrees Centigrade, or above) for from about 5 toabout 25 minutes. In one preferred embodiment, the soak time used isfrom about 5 to about 15 minutes.

Thereafter, the substrate is preferably cooled to ambient over a periodof from about 5 to about 30 minutes and, more preferably, from about 10to about 20 minutes.

The cooled substrate is then preferably dipped into a solution of"Posiclean A", an acid, organic, water-soluble cleaner sold by the RBPChemical Corporation of 150 south 118th Street, Milwaukee, Wis. Thismaterial is strongly acidic (with a pH of 0.7), and it removes thecopper oxide layer from the surface of the board.

FIG. 8A is a sectional view of a ceramic substrate 90 preferablycomprised of alumina 99 which is comprised of through holes 92 and 94.It is preferred that through holes 92 and 94 be substantially circularin cross-section and have a diameter of from about 2 to about 50 mils;it is preferred that the diameter of the vias be from about 10 mils toabout 20 mils. In one embodiment, the diameter of the through holes isfrom about 8 to about 17 mils and, more preferably, from about 14 toabout 16 mils. In one preferred embodiment, the diameter of the viaholes is from about 9 to about 12 mils.

For simplicity of representation, only two through holes 92 and 94 havebeen illustrated in FIG. 8A. It is preferred, however, for each 2"×2.75"section of substrate, that there be at least about 11 such through holesand, more preferably, be at least about 47 such through holes.

In one preferred embodiment, the substrate 90 is heated to a temperaturehigh enough to produce incipient fusion on the walls of the via holes.Thus, the alumina substrate may be heated to a temperature of from about1,200 degrees Centigrade to about 1,550 degrees Centigrade (andpreferably from about 1400 degrees Centigrade to about 1450 degreesCentigrade) over a period of from about 4 to about 40 hours, held atthis incipient fusion level for from about 1 to about 3 hours, and thenpermitted to cool to ambient temperature over a period of from about 4to about 40 hours. Although applicants do not wish to be bound to anyparticular theory, they believe that this heat-treatment of thesubstrate thermally etches it and causes glassy components of thealumina substrate to be removed from it, thereby roughening the surfaceof the alumina substrate. This thermal etching process may be used inaddition to, or instead of, the phosphoric acid etching processdisclosed in U.S. Pat. No. 5,058,799.

Referring again to FIG. 8A, the thickness 96 of substrate rate 90 ispreferably from about 10 mils to about 0.5 inches or more. It ispreferred, however, that thickness 96 be from about 20 mils to about 30and, more preferably, be from about 24 mils to about 26 mils.

FIG. 8B illustrates ceramic substrate 8A after a layer 98 of electrolesscopper has been deposited on the substrate by conventional means. Thus,for example, the copper may be electrolessly deposited by the meansdisclosed in U.S. Pat. No. 5,058,799. It is preferred that the layer 98of electroless copper be from about 40 to about 50 microinches thick.

After the electroless deposition of copper, a photomask (not shown) isput onto the electroless copper layer 98 by conventional means.Thereafter, referring to FIG. 8C, a layer 100 of electrolytic copper isselectively electroplated onto the exposed portions 98 of theelectroless copper.

The layer 100 of electrolytic copper consists essentially of copper andhas a thickness of at least about 3.5 mils. It is preferred that layer100 have a thickness of from about 4 to about 20 miles and, morepreferably, from about 5 to about 7 mils.

It is preferred that the conductive metal deposited onto the ceramicsubstrate have a thickness which is at least about 0.3 times as great asthe thickness of the ceramic substrate.

FIG. 8D illustrates the substrate 90 after it has been fired at atemperature higher than the eutectic temperature of copper and oxygenbut below the melting point of copper. In general, the temperature ofsuch firing is from about 1065 to about 1075 degrees Centigrade; see,e.g., U.S. Pat. No. 5,058,799.

It is believed that this firing causes diffusion of a eutectic melt andthe production of heterogeneous juncture bond 102 between the ceramic 99and the copper. As is indicated in U.S. Pat. No. 5,100,714, saidheterogeneous juncture bond 102 has a metal-wetted surface area that isat least about twice the apparent surface area of the metal layeroverlying the juncture bond and consists essentially of ceramic grainsunitary with the workpiece and conductive metal unitary with theconductive metal layer, and being constituted by finger-like metalprotuberances unitary with the metal layer and occupying the spacebetween the ceramic grains.

Because of the unique combination of processing steps used to makesubstrate 90, this metal-ceramic composite is capable of withstandingrepeated firing cycles at a tempera ture in excess of 850 degreesCentigrade without separation of the copper layer from the workingsurface of the alumina workpiece.

Referring again to FIGS. 8A, 8B, 8C, and 8D, the vias 92 and 94 arepreferably completely filled. Thus, at a magnification of 200 times(and, preferably, at a magnification of 1000 times), there are novisible voids.

In one embodiment, in order to improve the hermeticity of the substrate,the metalized substrate of FIG. 8C is lapped and ground to leave the viaholes 92 and 94 flush with the major surfaces of the 91 and 93 of thealumina substrate (see FIG. 8A). Thereafter, the lapped surfaces areagain subjected to electroless deposition (see FIG. 8B), electrolyticdeposition (see FIG. 8C), and heating to facilitate eutectic bonding(see FIG. 8D).

In one embodiment, illustrated in FIG. 9, the electrolytic deposition ofcopper (see FIG. 8C) creates a series of vent holes extending from thetop of the electrolytic copper layer 100 to the bottom of substratesurface 99. As will be apparent to those skilled in the art, theelectrolytic deposition pattern is determined by the photomask used.Alternatively, one can create such vent holes by other conventionalmeans such as, e.g., laser drilling, manual drilling, etc.

The vent holes are generally from about 5 mils to about 25 mils indiameter. In one embodiment, they range from about 18 to about 22 milsin diameter. The vent holes may all have the same diameters, ordifferent sizes and/or concentrations of vent holes may be used ondifferent portions of the board.

It is preferred to have at least about 100 vent holes per square inch ofmetalized substrate. Thus, some typical vent hole arrangements areillustrated in FIG. 3; see vent holes 110.

FIG. 9 is a partial sectional view of substrate 90 with showing venthole 110 and filled via 92.

In one embodiment, illustrated in FIG. 10, the metalized substrate ofFIG. 9 is printed with a copper paste/ink such as, e.g., DuPont's QP153conductor paste. This paste, and similar pastes, generally contain atleast about 80 weight percent of particulate copper grains in solventsand binders.

The printed metalized substrate is then fired in inert gas (such asnitrogen) containing from about 5 to about 25 parts per million ofoxygen (and preferably from about 5 to about 10 parts per million ofoxygen) at a temperature of from about 800 to about 970 degreesCentigrade; in one embodiment, a temperature of from about 895 to about905 degrees Centigrade is used. This firing is done in order to burn outthe organic material and to fuse the copper to the electrolytic copperlayer 100; see FIG. 10. The copper paste 112 fills the vent hole 110.

In the next step of the process, a screen-printed layer of glass pasteis selectively deposited over the top surface of the substrate,especially where circuits have to be protected. Thereafter, this screenprinted substrate is heated in a furnace under nitrogen atmosphere at atemperature sufficient to melt the glass onto the copper, therebycreating a layer 113 of glass which is generally from about 1 to about 7mils thick. One may use DuPont's 5681 glass ("dielectric) compositionfor this purpose, which may be fired at a temperature of from about 900to about 990 degrees Centigrade.

In one embodiment, the dielectric shown has a coefficient of thermalexpansion which substantially matches the coefficient of thermalexpansion of the metallized copper. As is known to those skilled in theart, a desired coefficient of thermal expansion of a dielectric materialcan be engineered to certain predetermined values by utilizingcomponents which have different coefficients of thermal expansion. Thus,as is disclosed in U.S. Pat. No. 5,224,017 (the disclosure of which ishereby incorporated by reference into this specification), a heatconductive member can be comprised of a first material having a positivecoefficient of thermal expansion and a second material having a negativecoefficient of thermal expansion. The first and second materials can becombined in a quantity ratio to produce a composite heat transfer devicewith a coefficient of thermal expansion which can be closely tailored tomatch the predetermined coefficient of thermal expansion of the objectwith which heat is to be transferred.

In the next step of the process, not shown, the electronic parts for thepower board are mounted thereon by conventional surface mountingtechniques such as, e.g., reflow methods. See, for example, U.S. Pat.Nos. 5,378,656, 5,347,162, 5,150,197, and the like; the entiredisclosure of each of these patents is hereby incorporated by referenceinto this specification.

The power board produced by the process of this invention has anunexpectedly advantageous combination of property.

The thermal conductivity of the board is measured based upon the squareinches of surface area. Thus, a board which has dimensions of 7"×5"×25mils will have its thermal conductivity measured as a function of the 35inches of surface area it has.

In general, the board preferably has a power handling capability of atleast about 23 watts per square inch of surface area. That is, the totalpower output of the board (device forward voltage×device current, foreach die summed) divided by the surface area is at least 23 watts persquare inch.

The power board also has a resistivity, as measured across of the topsurface of the board, of less than 0.0017 ohms. As is known to thoseskilled in the art, this value is close to the resistivity of copper.

The power board also preferably has a current carrying capacity of atleast from about 1900 to about 2000 amperes per 900 watts, as determinedby the voltage divided by the resistance of the copper trace.

Another Preferred Embodiment of the Invention

FIGS. 13-19 illustrate another preferred embodiment of the inventionwhich is more efficient than the embodiment depicted in FIGS. 1-12.

FIG. 13 is a top view of a preferred power board 300 used in thisembodiment. The embodiment depicted in FIG. 13 is similar to theembodiment depicted in FIG. 3 (and described elsewhere in thisspecification) with the exception that its layout is somewhat different.

FIG. 14 is a schematic diagram of the preferred power board of FIG. 13which is very similar to the power board depicted in FIG. 4 anddescribed elsewhere in the specification. It differs from the embodimentof FIG. 4 in that it contains a circuit protection unit 302 comprised ofa zener diode 304 connected to ground 306. As will be apparent to thoseskilled in the art, any reverse voltage spikes that might damage thecircuitry are passed to ground 306.

FIG. 15 is a schematic diagram of a preferred controller of the powersupply of FIG. 13. As will be apparent to those skilled in this art,this controller differs from the controller depicted in FIG. 5 in thatit has a different signal conditioning unit 308 and a differenttransistor driver 310.

Referring to FIG. 15, it will be seen that, in the preferred embodimentdepicted, signal conditioning unit 308 is comprised of double diode Dlwhich, as will be apparent to those skilled in the art, eliminatesvoltage spikes in the direction of arrow 309. This voltage spike filterprevents noise triggering of the U4 operational amplifiers.

Referring again to FIG. 15, and in the preferred embodiment depictedtherein, noise suppressor 311 also is utilized to control voltage spikesflowing in the direction of arrow 313.

FIG. 15A is the power supply of the controller of FIG. 15. This powersupply is identical to the power supply depicted in FIG. 5A.

FIG. 15B is the clock of the controller of FIG. 15. This clock issimilar to the clock depicted in FIG. 5, with the exception that itcontains an added higher current Darlington transistor 312.

FIG. 15C is the voltage control circuitry of the controller of FIG. 15.The voltage control circuitry is similar to the voltage controlcircuitry depicted in FIG. 15 with the exception that it contains addedsignal conditioning components 308, and that it does not voltagedividers R48, R49, and R47.

FIG. 16 is a schematic of the driver circuitry of the controller of FIG.15.

FIG. 17 is top view of another preferred controller board of thisinvention which is similar to the controller board of FIG. 6 but differsin its layout of components.

FIG. 18 is a top view of a preferred panel containing four power boardsof this invention. The panel depicted in FIG. 18 is similar the paneldepicted in FIG. 7 but has a different physical layout of components.

FIG. 19 is a top view of an individual power board made in accordancewith this invention which has a different physical layout of circuitsand location of through holes. Referring to FIG. 19, it will be seenthat power board 314 is comprised of a multiplicity of completely filledvias 316. In one embodiment, completely filled vias 316 has no visiblevoids at a magnification of 200×. In another embodiment, completelyfilled vias 316 have no visible voids at a magnification of 1000×.

It is to be understood that the aforementioned description isillustrative only and that changes can be made in the apparatus, in theingredients and their proportions, and in the sequence of combinationsand process steps, as well as in other aspects of the inventiondiscussed herein, without departing from the scope of the invention asdefined in the following claims.

We claim:
 1. A miniature power supply and voltage regulator comprised ofa ceramic substrate comprising a top surface and bottom surface, a firstlayer of conductive metal bonded to said top surface, and a second layerof conductive metal bonded to said bottom surface, wherein said powersupply and voltage regulator is comprised of a first means forconverting alternating current to direct current, a second means forconverting alternating current to direct current, a means fordetermining the current demands of a load, and a means for deliveringsaid current demands to said load, wherein:(a) said power supply andvoltage regulator has a power handling capacity of at least 23 watts persquare inch of surface area of said top surface, (b) a firstheterogeneous juncture band exists between said first layer ofconductive metal and said top surface, (c) a second heterogeneousjuncture band exists between said second layer of conductive metal andsaid bottom surface, (d) each of said first heterogeneous juncture bandand said second heterogeneous juncture band has a metal-wetted surfacearea that is at least about twice the apparent surface area of thecopper overlying the juncture band and consists essentially of ceramicgrains unitary with said ceramic substrate and conductive metal unitarywith said copper layer and being constituted by finger-like copperprotuberances unitary with the copper layer and occupying the spacesbetween the ceramic grains of said ceramic, (e) said ceramic substratehas a thickness of at least about 10 mils, (f) each of said first layerof conductive metal and said second layer of copper has a thickness ofat least about 3.5 mils and is comprised of at least about 98 weightpercent of conductive metal, (g) the thickness of each of said firstlayer of conductive metal and said second layer of conductive metal isat least 0.3 times as great as the thickness of said ceramic substrate,(h) said power supply and voltage regulator is comprised of a noisesuppressor circuit, (i) said power supply and voltage regulator iscomprised of at least six silicon controlled rectifiers, (j) said powersupply and voltage regulator is comprised of a multiplicity of diodes,and (k) said silicon controlled rectifiers and said diodes are surfacemountable components in bare die form.
 2. The power supply as recited inclaim 1, wherein said ceramic is beryllia.
 3. The power supply asrecited in claim 1, wherein said ceramic is alumina.
 4. The power supplyas recited in claim 3, wherein said conductive metal is copper.
 5. Thepower supply as recited in claim 4, wherein said alumina substrate has athickness of from about 20 to about 30 mils.
 6. The power supply asrecited in claim 5, wherein each of said first layer of copper and saidsecond layer of copper has a thickness of at least about 6 mils.
 7. Thepower supply as recited in claim 6, wherein said alumina substrate iscomprised of a multiplicity of through holes extending from said topsurface of said substrate to said bottom surface of said substrate. 8.The power supply as recited in claim 7, wherein each of said throughholes is completely filled so that, at a magnification of 200 diameters,no visible voids appear.
 9. The power supply as recited in claim 7,wherein at least about 100 vent holes per square inch are disposedwithin said top layer of copper and said bottom layer of copper.
 10. Thepower supply as recited in claim 9, wherein each of said vent holes hasa diameter of from about 5 mils to about 25 mils.
 11. The power supplyas recited in claim 10, wherein each of said vent holes has a diameterof form about 18 mils to about 22 mils.
 12. The power supply as recitedin claim 10, wherein a first layer of dielectric material is disposedover and contiguous with said first layer of copper.
 13. The powersupply as recited in claim 12, wherein said first layer of dielectricmaterial is comprised of a first material with a positive coefficient ofthermal expansion and a second material with a negative coefficient ofthermal expansion.
 14. The power supply as recited in claim 13, whereinsaid first layer of dielectric material has a coefficient of thermalexpansion which is substantially identical to the coefficient of thermalexpansion of said first layer of copper.